1. Field of the Invention
The present invention relates to an ink-jet printing ink suitable for use in conducting textile printing, in particular, on woven or nonwoven fabrics of cotton, silk or the like, which are dyeable with reactive dyes and composed principally of cellulose fibers and/or polyamide fibers, or mixed woven or nonwoven fabrics composed of these fibers and other fibers, and an ink-jet printing process and an instrument making use of the ink.
2. Related Background Art
At present, textile printing is principally conducted by screen printing or roller printing. Both methods are unfit for multi-kind small-quantity production and difficult to quickly cope with the fashion of the day. Therefore, there has recently been a demand for development of an electronic printing system making no use of any plate.
In compliance with this demand, many textile printing processes according to ink-jet recording have been proposed. Various fields expect much from such textile printing processes.
Ink-jet printing inks are required to have the following performance characteristics:
(1) being able to develop the color of ink to a sufficient color depth after conducting washing; PA1 (2) causing no clogging in an ejection orifice; PA1 (3) being able to quickly dry on cloth; PA1 (4) undergoing little irregular feathering on cloth; PA1 (5) undergoing no changes in physical properties and ejection properties and depositing no solid matter in the course of storage; and PA1 (6) undergoing no change in ejection properties even in a long-time ejection durability test, and causing neither disconnection nor deposition of foreign matter on a heating head, in particular, in a case of textile printing by a system making use of thermal energy.
In order to satisfy these performance characteristics required, the following means have heretofore been proposed.
First, in order to cope with the requirement (1), it has been generally conducted to make the concentration of a dye sufficiently high. This method is an essential means for using ink droplets as minute as 200 pl or less, or conducting textile printing on a cloth high in absorbing power. However, such an ink causes a problem of thickening due to evaporation of water in the ink and the problem as to the requirement (2) because of deposition of the dye as solid matter.
It has therefore been conducted to add a polyhydric alcohol such as glycerol to an ink in order to cope with the requirement (2). However, this means is not useful if the concentration of a dye contained in the ink exceeds 5%, and hence does not give a satisfactory result except for the case of an extremely specific combination of dye and solvent.
No particular problem is offered to the requirement (3), which is greatly affected by the water repellency of a cloth to be used, so far as a water-based ink is used for a cloth composed mainly of cellulose fibers and/or polyamide fibers.
In order to cope with the requirement (4), many proposals such as addition of, for example, tannin (Japanese Patent Application Laid-Open No. 61-231289) or a carboxyl group-containing polymer (Japanese Patent Application Laid-Open No. 62-283174) to an ink have been made. However, both proposals can not avoid the problems of the requirements (1) and (2) arising from ink.
With respect to the requirements (5) and (6), close investigations have not been conducted under the circumstances because an improvement may be made on the basis of the structure of dye or by additives.
In the field of textile printing, there has been a demand for dyeing cloths of different kinds. However, the optimum composition of an ink varies with individual cloths. More specifically, a dye to be used greatly varies in kind and even fixing conditions thereof depending upon the dyeing mechanism between dye and cloth, which is an ionic bonding, a covalent bonding or a simple diffusion of the dye into fibers. In addition, since polyester and cellulosic fibers considerably differ from each other in affinity for water, the design of the whole liquid medium including additives must be devised if printing is conducted with a water-based ink on cloths formed of such fibers. Accordingly, technical problems required of inks vary little by little depending upon cloths to be printed, so that individual designs are required for inks.
Means capable of satisfying one of the above requirements have been able to be found in the prior art. However, there has not yet been known any printing ink satisfying all the above-mentioned requirements at the same time.